This invention relates to drain structures for aircraft.
During flight the cabin of a commercial aircraft will generally be pressurized, and temperatures outside the aircraft will be substantially lower than those inside. These differences in temperature and pressure between the inside of the aircraft and the ambient are necessary to protect cargo and ensure the comfort and safety of passengers and crew.
In most cases the outside walls or skin of a commercial aircraft are thermally insulated and sealed against fluid leakage so that the temperature and pressure within the aircraft fuselage may be efficiently maintained within permissible limits. As a result, there will usually be a substantial quantity of liquid condensate produced within the fuselage during a flight, and this liquid can present a serious problem if not properly disposed of.
One method of dealing with liquid condensate accumulated within the aircraft fuselage during a flight involves draining any such liquid from the fuselage through appropriately located drains. Since the aircraft fuselage must remain sealed while the cabin is pressurized, the drains must be easily opened and closed. Drains which open and close automatically in response to changes in the pressure differential between the inside and the outside of the fuselage may be designed to be self-sealing whenever the cabin is pressurized and to allow discharge of liquid condensate immediately upon cabin depressurization.
Although such drains have the advantage of requiring little or no attention from flight crew personnel, experience has shown that debris from inside the cabin tends to find its way to these drains and interfere with their operation. This debris will frequently clog the individual drains and may both interfere with drainage when the drain is open and interfere with closing of the drain when the cabin is pressurized.
Thus a drain apparatus is needed which will not only open and close automatically but will also be self-cleaning.